Stereo apparatus that includes a master unit and a slave unit

ABSTRACT

An apparatus for providing sound in vehicles which comprises a receiver for radio frequency waves with frequency selection and antenna. The apparatus includes a master unit located in the vehicle close to the driver&#39;s seat including loud-speakers. The apparatus also includes a slave unit which is located together with the antenna remotely from the master unit. The slave unit includes a circuit controlled from the master unit for selecting a desired frequency and converting the selected signal into an intermediate frequency. The master unit also includes a detector, a pre-amplifier and a power amplifier along with controls for adjusting the receiver.

TECHNICAL FIELD

The present invention concerns an apparatus for providing sound invehicles, comprising a receiver for radio-frequency waves with frequencyselection, an antenna connected to said receiver, an operating meanslocated in the vehicle close to the driver's seat including a poweramplifier with controls for adjusting the sound volume, and loudspeakersconnected to said power amplifier.

BACKGROUND OF THE INVENTION

Equipment for receiving radio waves and producing sound in vehiclesgenerally comprise a stereo radio-cassette. The available space is verylimited for the controls needed for programming the transmitterfrequencies, adjusting the sound or operating the tape player. Thisimplies that the control buttons can rarely be of an advantageouslyergonomic design. The stereo radio-cassette is often completed with aCD-switcher placed in the luggage compartment of the vehicle, whichrequires an extra operating unit on the operating panel for controllingthe CD-switcher.

The radio antenna generally has to be placed at such a long distancefrom the radio unit that a separate antenna amplifier is needed. It iseven known to place the whole radio unit near to an antenna in the rearpart of the car, e.g. as in U.S. Pat. No. 4910796, and to transmit theLF-signal to a power amplifier at the operating part in the operatingpanel. This then necessitates several conductors to transmit stereosignals, and also a conductor to transmit the station selection signal.

Vehicle manufacturers are also faced with a problem to integrate evermore technically complicated sound systems in the environment of thedriver. Owing to the RDS-technique, the car radio is used to an evergreater extent for receiving traffic messages. A substantial problem forvehicle suppliers is that different markets, like western Europe, USA,Australia, Japan and eastern Europe, make use of different frequencybands for radio reception, and development goes a way where new digitaltransmission techniques also end up on different frequency bands. Thecosts to supply different markets with different system variants getvery high. Furthermore, the costs to install these systems in a vehicleare high.

TECHNICAL PROBLEM

The purpose of the present invention is therefore to attain an apparatusfor providing sound in vehicles, which simplifies the adaptation todifferent markets by reducing both the costs for the hardware requiredto offer different system variants and the installation need after thevehicle has left the assembling factory as well.

SOLUTION

For this purpose, the invention is characterized in, that said radioreceiving means is divided into a master unit close to the driver's seatin the vehicle, and a slave unit which is located together with theantenna remotely from said master unit, said slave unit comprises acircuit controlled from said master unit for selecting a desiredtransmitter frequency and a circuit for converting the selected signalinto a signal of intermediate frequency with mainly a constantfrequency, and said master unit comprises a detector, a pre-amplifierand said power amplifier along with controls for adjusting the receiver.

DESCRIPTION OF THE DRAWINGS

The invention will be described herebelow with reference to thepreferred embodiment which is shown on the accompanying drawings wherein

FIG. 1 schematically shows a vehicle with the apparatus of the inventionin a perspective view, and

FIG. 2 is a block diagram which schematically shows a sound equipmentfor a vehicle designed according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The vehicle 10 shown in FIG. 1 is equipped with a window pane antenna 11mounted on the left rear window pane. The antenna is connected to aslave unit 12 placed relatively close to the same. This slave unit formsa radio receiving means which is in turn connected through a coaxialcable 13 to a master unit 14 placed in the vehicle close to the driver'sseat with an operating panel that preferably comprises a poweramplifier, a tape player and controls for adjusting the loudspeakers 15,as well as controls for programming and selecting radio channels.

FIG. 2 shows schematically the design of the equipment. The slave unit12 comprises a high frequency amplifying block 16 for a desired radioband even in a RDS-application, a mixer 17, an oscillator 18 and anintermediate frequency amplifier 19. The master unit 14 near by thedriver's seat comprises a stereo decoder and an electronic noisesuppressor as well as a pre-amplifier.

By placing the high frequency receiving block 16 near the antenna 11, anantenna cable which damps the signal is avoided, so that the need for aseparate antenna amplifier disappears. The intermediate frequency, e.g.for VHF 10.7 MHz, that is transmitted between the slave unit and themaster unit, is not appreciably attenuated in the coaxial cable 13. Theinterference distance becomes large since the signal from theintermediate frequency amplifier can be put on a level insensitive todisturbances. For AM reception, an intermediate frequency around 450 kHzis normally used. It will, contrary to the case where a long antennacable is used and a compromise has to be done between exigences for FMor AM reception, be easy to optimize the coaxial cable impedance.Besides, the number of conductors will be less compared with atransmission of a demodulated low frequency signal in stereo.

FIG. 2 also shows a CD-switcher 20 which can be equipped with a 10.7 MHzoutput, so that it can be connected to the master unit 14 through thecoaxial cable 13. The technique for remotely controlling the slave unit12 and the CD-switcher 20 is already known and is based on serial dataand clock pulse, to keep the number of cables low. Microprocessors forthis purpose are available on the market in simple and cheap designs. Byusing a digital/analog converter, the signal transmission can de donedirectly through the coaxial cable 13.

The slave unit can be supplied in different designs for differentmarkets. In that way, the remaining equipment can be common to allmarkets. This gives obvious advantages like savings despite the greatvariety of models, and simplifies design changes for different year orcar models.

If needed, several slave units can be combined, for example a slave unitfor normal RDS-reception and an other slave unit which is intended forreceiving Digital Audio Broadcasting. In DAB, the digital signal can beconverted in an interface to a 10.7 MHz intermediate frequency signal.For certain markets, it may even be interesting to complete a slave unitfor receiving the short wave band.

The slave unit can be mounted hidden behind some detachable panel in theluggage compartment. The slave unit assembly can be done in an easy wayby the final user on the actual market, whereas all remaining equipmentcan be factory-assembled. The same slave units can be used for differentcar makes. The placing of the slave unit simplifies and reduces thecosts for service and when upgrading. An exchange system can be builtup, which further reduces the customer's costs. Use of a certain slaveunit makes it cheaper to exchange the master unit when connecting toanother sound source like Mini-Disk, DCC, DAT or CD-switcher 20.

FIG. 2, also illustrates the possibility to remotely control the masterunit 14 by way of a remote control 21, which is equipped with controlssuch as volume control 22, function selection 23, station selection 24and presets 25. This variant may be interesting for limousines and taxisas an example.

Same types of slave units according to the invention can be used withdifferent systems of master units, which can be adapted to interiors andcurrent conditions in busses, lorries and boats.

The invention is not limited to the embodiments hereinbefore described,which may be modified within the scope of the appended claims.

I claim:
 1. Stereo apparatus for providing sound in vehicles comprisinga receiving means for radio-frequency waves with frequency selection, anantenna connected to said receiving means, an operating means located inthe vehicle close to the driver's seat including a power amplifier withcontrols for sound adjustment, and loudspeakers connected to said poweramplifier, wherein said receiving means is divided into a master unitclose to the driver's seat in the vehicle, and a slave unit which islocated together with the antenna remotely from said master unit, saidslave unit comprising a circuit controlled from said master unit forselecting a desired transmitter frequency signal that includes a stereosignal, a mixer, an oscillator, and a circuit including an intermediatefrequency amplifier for converting the selected stereo signal into asignal of intermediate frequency with mainly a constant frequency, andsaid master unit comprising a detector, a stereo decoder and apre-amplifier.
 2. Stereo apparatus according to claim 1, wherein saidmaster unit and said slave unit are equipped with a micro-computerinterface for reciprocal data communication.
 3. Stereo apparatusaccording to claim 2, wherein data communication between said masterunit and said slave unit is serial.
 4. Stereo apparatus according toclaim 2, wherein said slave unit and said master unit are linked througha coaxial cable.
 5. Stereo apparatus according to claim 1, wherein datacommunication between said master unit and said slave unit is serial. 6.Stereo apparatus according to claim 5, wherein said slave unit and saidmaster unit are linked through a coaxial cable.
 7. Stereo apparatusaccording to claim 1, wherein said slave unit and said master unit arelinked through a coaxial cable.
 8. Stereo apparatus according to claim1, wherein said master unit includes connection means for connecting themaster unit to other sound source.